Dating waiting intervals

Mainly because little safety or efficacy data exist on doses given before 6 weeks of age, and the vaccines aren't licensed for this use.

If the vaccine is a live vaccine, ensuring that a minimum interval of 28 days has elapsed from the invalid dose is recommended.Alternatively, one can perform serologic testing to check for immunity, but this option may be more costly, may not be practical if multiple antigens are involved (such as measles, mumps and rubella), and may provide results that are difficult to interpret.If vaccines are given too close together, it can result in a less than optimal immune response.However, if a dose was administered 5 or more days earlier than the recommended minimum interval between doses, it is not valid and must be repeated.The repeat dose should be spaced after the invalid dose by the recommended minimum interval.